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These are what the chromosomes of a human look like. Chromosome pairs like these are in every human cell. The last pair determines the gender of the person. Courtesy of the National Library of Medicine and NIH

Chromosomes, DNA and Genes: Tiny Things That Have a Huge Effect on Who We Are!

Do you look a bit like your brothers or sisters? Do you look a bit like your parents? You may look alike because, unless you were adopted, you and the other members of your family have genes in common.

Genes are the instructions that tell your body how is should be built and what it can do. An organism has the same genes for its entire life.

Where are those genes? They are very tiny! Genes are located in the center of each cell in tiny but complex molecules called chromosomes. There are many genes within each chromosome. The chromosome molecules contain all sorts of information about what makes you special and different from everyone else. All living things that have eukaryotic cells, such as dogs, butterflies, and fish, have chromosomes in their cells. Chromosomes come in pairs. In your body, one chromosome of each pair came from your mother and one came from your father.

For each gene there can be many varieties. In your body, there are two varieties of the same gene. One came from your mother and the other came from your father. The two varieties do not always contain the same instructions. For instance, one variety might tell the body that eyes should be blue while another variety tells that eyes should be brown. The dominant gene determines the actual color of the person's eyes.

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